The PTC device as described above is widely used as a protection device to protect electrical elements constituting various electrical apparatuses, for example a secondary battery cell, or circuits constituting electrical apparatuses when an excessive current flows through the electrical apparatuses. The PTC device is also widely used as a protection device to interrupt an electrical current flowing through the electrical apparatus when the electrical element fails, as a result of which a temperature of the electrical apparatus rises abnormally high.
Such PTC device is disclosed, for example, in the Patent Reference 1 shown below, an example of which is shown in FIG. 8 as a schematic cross-sectional view. The PTC device 200 comprises a PTC component 212 and a first insulation layer 214a and a second insulation layer 214b which are disposed on both sides thereof. The PTC component 212 comprises a PTC element 210 and a first laminar electrode 212a and a second laminar electrode 212b which are disposed on both sides thereof. The laminar electrode 212a is connected to a first side electrode 220, and the laminar electrode 212b is connected to a second side electrode 222. In the PTC device, the first side electrode 220 and the second side electrode 222 are formed of metal plated layers.
The first side electrode 220 is formed by integrating, in addition to an electrode section present at one end of the PTC element 210 along its thickness direction, an electrode section 216 which is positioned on a section of said one end of the first insulation layer 214a and an electrode section 216 which is positioned on a section of said one end of the second insulation layer 214b together. The second side electrode 222 is formed by integrating, in addition to an electrode section present at the other end of the PTC element 210 along its thickness direction, an electrode section 218 which is positioned on a section of said other end of the first insulation layer 214a and an electrode section 218 which is positioned on a section of said the other end of the second insulation layer 214b together. The intermediate regions between the electrode sections 216 and 218 are coated with solder masks 224a and 224b (insulating bodies).
U.S. Pat. No. 6,377,467 is a prior patent reference.